private void Match(TK kind)
{
if (next < limit && Tokens[next].Kind == kind)
{
next += 1;
return;
}
Errors.AtToken(ErrNo.Scan001, Current, $"unknown token in token stream, expected ``{Keywords.String(kind)}´´ but got ``{Keywords.String(Current.Kind)}´´");
throw new NotImplementedException();
}
public Unit ParseUnit()
{
next = 0;
var unit = Unit();
if (!Is(TK.Eof))
{
Errors.AtToken(ErrNo.Scan002, Current, "inconclusive parse, not at ``EOF´´");
}
return(unit);
}
private IExpression?TryInfix(bool next = false)
{
Begin();
var term = TryTerm(next);
if (term != null)
{
var op = BinaryOp();
if (op == Tree.BinaryOp.As)
{
var types = new List <(BinaryOp op, IType ty)>();
do
{
MatchAny();
var nextType = Type();
types.Add((op, nextType));
}while ((op = BinaryOp()) != Tree.BinaryOp.Missing);
var operators = types.Select(t => t.op).Distinct().ToList();
if (operators.Count >= 2)
{
var part = types.Where(p => p.op != operators[0]).Select(p => p.ty).First();
var token = Tokens[part.Span.Start];
Errors.AtToken(
ErrNo.Scan002,
token,
"binary operators have no precedence, use ( ) to group binary expressions");
}
var operands = types.Select(t => t.ty).ToList();
return(new As(End(), term, operands));
}
if (op != Tree.BinaryOp.Missing)
{
var terms = new List <(BinaryOp op, IExpression ex)>();
do
{
MatchAny();
var nextTerm = Term();
terms.Add((op, nextTerm));
}while ((op = BinaryOp()) != Tree.BinaryOp.Missing);
var operators = terms.Select(t => t.op).Distinct().ToList();
if (operators.Count >= 2)
{
var part = terms.Where(p => p.op != operators[0]).Select(p => p.ex).First();
var token = Tokens[part.Span.Start];
Errors.AtToken(
ErrNo.Scan002,
token,
"binary operators have no precedence, use ( ) to group binary expressions");
}
var @operator = operators[0];
var operands = Enumerable.Repeat(term, 1).Concat(terms.Select(t => t.ex)).ToList();
return(new Binary(End(), @operator, operands));
}
}
return(Scrap(term));
}
private Exception Expected(string what)
{
Errors.AtToken(ErrNo.Scan004, Current, $"can't parse ``{what}´´, at token ``{Keywords.String(Current.Kind)}´´");
return(new NotImplementedException());
}